A device and a tube of the kind set forth are known from a leaflet published by Applicant and entitled "High Power X-ray Diffraction Tubes". The leaflet discloses an X-ray tube in which water is used as the cooling liquid for the anode. The conduit means for the supply and discharging of the cooling water comprise a cooling water inlet, denoted therein as "Water in" and a cooling water outlet which is denoted therein as "Water out", a duct which conducts the cooling water along the anode to be cooled being provided between the inlet and outlet. The inlet and the outlet are both provided in a flange arranged on the tube at the area of an end which is situated in the vicinity of the anode to be cooled. The X-ray tube is secured and positioned in the holder by means of the flange. The cooling water is supplied and discharged via openings in an abutment in the holder, which openings correspond to the inlet and the outlet in the flange. In the X-ray tube shown in this publication a line-shaped X-ray focus is formed wherefrom the radiation can be taken off in two mutually perpendicular directions, i.e. in the longitudinal direction of the focus and in a direction perpendicular thereto. For each of these directions an exit window is provided in the X-ray tube.
For some X-ray diffraction applications it is desirable to expose the specimen to be examined from a line-shaped focus, whereas for other applications a point-shaped focus is to be preferred. Therefore, the X-ray tube preferably provides both focus shapes. In the known X-ray tube this is possible by taking off the X-rays in the longitudinal direction of the focus line at a small angle relative to the anode surface; the line focus is then seen as a (virtual) point focus. When the X-rays are taken off in a direction perpendicular to the longitudinal direction, the X-ray focus is seen to be line-shaped. In practice the direction for the X-rays is prescribed, because this direction defines the location of the specimen, the detectors and the other equipment of the analysis apparatus. The desired switching-over from point focus to line focus and vice versa is then realised by rotating the X-ray tube in the holder through one quarter of a turn.
Rotation of the X-ray tube in its holder, however, has the drawback that after rotation the location of the openings in the abutment in the holder no longer registers with the inlet and the outlet in the flange of the X-ray tube. It would be feasible to solve this problem by providing an adapter flange between the flange of the tube and the abutment in the holder, i.e. one adapter flange for each position of the tube. The holes present in the abutment could then register once more with the holes in the tube flange. It is a drawback of this solution, however, that it requires separate components (the adapter flanges) and that such an exchange can be performed by skilled personnel only. It is a further drawback of this method of supplying water to the tube that a given amount of water is inevitably released near the high-voltage connector when the tube is detached for rotation. The water could cause high-voltage flash-overs which damage the connector and/or the X-ray tube.